Numerous membrane separation processes are known wherein a material having different permeabilities to two materials is used to separate and/or concentrate a mixture of the materials. Some of these processes include diffusion control, gas separation, dialysis, ultrafiltration, osmosis, reverse osmosis, pervaporation, diasolysis, hemodialysis, piezodialysis and forced flow electrophoresis. These processes are well known and a good description is in Encyclopedia of Polymer Science and Technology Vol. 8, page 620, 1968. They all use a semipermeable membrane as the basic separation device although incorporating other features such as pressure, electrical assistance, etc., to speed or otherwise affect the separation. Membranes in these processes must not only have the desired morphology to achieve the appropriate separation but must process easily, have good mechanical properties and be stable in their environments.